In this kind of technical field, research and development on the next generation communication system is rapidly progressing. In the communication system considered as of now, from the view point of widening coverage while reducing PAPR (Peak-to-Average Power Ratio), it is proposed to use a single carrier scheme for uplink. In addition, in this communication system, for both of uplink and downlink, radio resources are properly assigned, as a form of a shared channel which is shared by a plurality of users, according to communication states of each user and the like. More particularly, a data signal of a user in the uplink is transmitted by a physical uplink shared channel (PUSCH). The terms “channel” and “signal” may be used synonymously as long as there is no fear of confusion. A data signal of a user in the downlink is transmitted by a physical downlink shared channel (PDSCH).
Processing for determining assignment is called scheduling. In order to properly perform scheduling in the uplink, each user apparatus transmits a reference signal (also called as a pilot channel) to a base station, and the base station evaluates the channel state of the uplink based on the reception quality. In addition, in order to perform scheduling in the downlink, the base station transmits a reference signal to the user apparatus, and the user apparatus reports to the base station information indicating channel state (CQI: Channel Quality Indicator) based on the reception quality of the reference signal. Based on the CQI reported from each user apparatus, the base station evaluates the channel state of the downlink to perform scheduling of downlink. The contents of scheduling are transmitted to each user apparatus by a downlink control signal. This control signal is called a downlink L1/L2 control channel or a downlink L1/L2 control signal.
As uplink control signals, there are control information (called first control information, for the sake of convenience) that should be transmitted by accompanying an uplink data signal, and control information (called second control information, for the sake of convenience) that is transmitted irrespective of the presence or absence of the uplink data signal. The first control information includes information necessary for demodulation of a data signal, such as modulation scheme, channel coding rate and the like of the data signal. The second control information includes CQI information of downlink channel, acknowledgement information (ACK/NACK) of downlink data signal, and information of resource assignment request, and the like. Therefore, there is a possibility that the user apparatus transmits only the first control information, only the second control information, or both of the first and the second control information by using the uplink control signal.
When a resource block (radio resource) is assigned for transmitting an uplink data channel, the first control information (and second control information as necessary) is transmitted by the resource block. On the other hand, when the uplink data signal is not transmitted, it is considered to transmit the second control signal by using dedicated resources (dedicated band). In the following, an outline of an example is described in which a band is used in such a way.
FIG. 1 shows a band use example of uplink. FIG. 1 shows resources (a plurality of resource blocks) for transmitting the physical uplink shared channel (PUSCH) that is the uplink data signal, and shows resources (corresponding to the dedicated band) for a user to which the resources for the PUSCH are not assigned to transmit the uplink control signal. The latter is called a physical uplink control channel (PUCCH). In the example shown in the figure, one or more of four resource blocks are assigned to users, and a first hopping control signal and a second hopping control signal are prepared in a transmission time interval (TTI), and a third hopping control signal and a fourth hopping control signal are prepared in the following TTI. Each hopping control signal corresponds to PUCCH. By performing hopping with respect to time and frequency in TTIs or subframes, diversity effect can be obtained. Each of the first to fourth hopping control signals may be occupied by one user or may be multiplexed by a plurality of users. This type of transmission scheme of the uplink control signals is described in the non-patent document 1.                [Non-patent document 1] 3GPP, R1-071245        